U.S. patent application number 17/352979 was filed with the patent office on 2022-02-10 for electric vehicle.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Hiroyuki AMANO, Hiroaki EBUCHI, Tatsuya IMAMURA, Yoichiro ISAMI, Yoshio ITOU, Hiroaki KODERA, Akiko NISHIMINE.
Application Number | 20220041065 17/352979 |
Document ID | / |
Family ID | 1000005710373 |
Filed Date | 2022-02-10 |
United States Patent
Application |
20220041065 |
Kind Code |
A1 |
ISAMI; Yoichiro ; et
al. |
February 10, 2022 |
ELECTRIC VEHICLE
Abstract
The electric vehicle according to the present disclosure is
configured to be able to select a traveling mode between an MT mode
in which an electric motor is controlled with torque
characteristics like an MT vehicle having a manual transmission and
an internal combustion engine, and an EV mode in which the electric
motor is controlled with normal torque characteristics. The
controller of the electric vehicle controls the electric motor in
the MT mode such that responsiveness of the motor torque with
respect to a change in the operation amount of the accelerator
pedal is lower than in the EV mode.
Inventors: |
ISAMI; Yoichiro;
(Mishima-shi, JP) ; ITOU; Yoshio; (Susono-shi,
JP) ; AMANO; Hiroyuki; (Susono-shi, JP) ;
IMAMURA; Tatsuya; (Okazaki-shi, JP) ; NISHIMINE;
Akiko; (Susono-shi, JP) ; EBUCHI; Hiroaki;
(Hadano-shi, JP) ; KODERA; Hiroaki; (Susono-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
1000005710373 |
Appl. No.: |
17/352979 |
Filed: |
June 21, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60Y 2300/60 20130101;
B60Y 2200/91 20130101; B60K 2026/025 20130101; B60L 15/20 20130101;
B60K 26/021 20130101; B60K 23/02 20130101 |
International
Class: |
B60L 15/20 20060101
B60L015/20; B60K 23/02 20060101 B60K023/02; B60K 26/02 20060101
B60K026/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2020 |
JP |
2020-135126 |
Claims
1. An electric vehicle configured to use an electric motor as a
power device for traveling, the electric vehicle comprising: an
accelerator pedal; a pseudo-clutch pedal; a pseudo-gearshift; a
mode selector configured to manually or automatically select a
control mode of the electric motor between a first mode and a
second mode; and a controller configured to control a motor torque
output by the electric motor in accordance with the control mode
selected by the mode selector, wherein the controller comprises: a
memory configured to store: an MT vehicle model simulating a torque
characteristic of a driving wheel torque in an MT vehicle having an
internal combustion engine whose torque is controlled by operation
of a gas pedal and a manual transmission whose gear stage is
switched by operation of a clutch pedal and operation of a
gearshift; and a motor torque command map defining a relationship
of a motor torque with respect to an operation amount of the
accelerator pedal and a rotation speed of the electric motor; and a
processor configured to execute: in the first mode, a process of
receiving an operation amount of the accelerator pedal as an input
of an operation amount of the gas pedal with respect to the MT
vehicle model, a process of receiving an operation amount of the
pseudo-clutch pedal as an input of an operation amount of the
clutch pedal with respect to the MT vehicle model, a process of
receiving a shift position of the pseudo-gearshift as an input of a
shift position of the gearshift with respect to the MT vehicle
model, a process of calculating the driving wheel torque determined
from the operation amount of the gas pedal, the operation amount of
the clutch pedal and the shift position of the gearshift using the
MT vehicle model, and a process of calculating the motor torque for
giving the driving wheel torque to driving wheels of the electric
vehicle; and in the second mode, a process of disabling the
operation of the pseudo-clutch pedal and the operation of the
pseudo-gearshift, and a process of calculating the motor torque
using the motor torque command map based on the operation amount of
the accelerator pedal and the rotation speed of the electric motor,
wherein the processor is configured to control the electric motor
in the first mode such that responsiveness of the motor torque with
respect to a change in the operation amount of the accelerator
pedal is lower than in the second mode.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority under 35 U.S.C.
.sctn. 119 to Japanese Patent Application No. 2020-135126, filed
Aug. 7, 2020, the contents of which are incorporated herein by
reference in their entirety.
BACKGROUND
Field
[0002] The present disclosure relates to an electric vehicle
configured to use an electric motor as a power device for
traveling.
Background Art
[0003] An electric motor used as a power device for traveling in an
electric vehicle differs greatly in torque characteristic from an
internal combustion engine used as a power device for traveling in
a conventional vehicle. Due to the difference in torque
characteristics of power devices, a transmission is essential for
the conventional vehicle, whereas in general the electric vehicle
is not equipped with a transmission. Of course, the electric
vehicle is not equipped with a manual transmission (MT: Manual
Transmission) that switches a gear ratio by manual operation by a
driver. Therefore, there is a great difference in a driving feeling
between driving of the conventional vehicle with the MT
(hereinafter referred to as MT vehicle) and driving of the electric
vehicle.
[0004] On the other hand, the torque of the electric motor can be
controlled relatively easily by controlling the applied voltage and
magnetic field. Therefore, the electric motor can obtain a desired
torque characteristic within an operating range of the electric
motor by implementing appropriate motor control. Taking advantage
of this feature, a technique to simulate the torque characteristic
peculiar to the MT vehicle by controlling the torque of the
electric vehicle has been proposed so far.
[0005] JP 2018-166386 discloses a technique for producing a pseudo
shift change in a vehicle that transmits torque to wheels from a
drive motor. In this vehicle, at a predetermined opportunity
defined by a vehicle speed, an accelerator opening, an accelerator
opening speed, or a brake depression amount, after reducing the
torque of the drive motor by a set variation amount, torque
variation control is performed to increase the torque again at a
predetermined time period. Thus, an uncomfortable feeling given to
a driver familiar with a vehicle equipped with a stepped
transmission is suppressed.
[0006] However, in the above technique, it is impossible to
determine the timing of executing the torque variation control
simulating the speed change operation voluntarily by the driver's
own operation. In particular, for the driver accustomed to driving
the MT vehicle, pseudo speed change operation without intervention
of manual speed change operation by the driver has a possibility
that a discomfort is given to the driving feeling of the driver
seeking pleasure to operate the MT.
SUMMARY
[0007] In view of such circumstances, the inventors of the present
application are considering providing a pseudo-gearshift and a
pseudo-clutch pedal on the electric vehicle so as to obtain a
feeling of driving the MT vehicle in the electric vehicle. Of
course, these pseudo-devices are not simply attached to the
electric vehicle. The inventors of the present application are
considering allowing the electric motor to be controlled by
operating the pseudo-gearshift and pseudo-clutch pedal so that the
torque characteristic similar to that of the MT vehicle can be
obtained.
[0008] Incidentally, whether torque response to accelerator
operation is high or low appears as a difference in the driving
feeling when the driver drives the vehicle. There is a clear
difference in the torque response to the accelerator operation
between the MT vehicle using an internal combustion engine as a
power device and the EV using an electric motor as a power device.
While the torque of the EV responds linearly to a change in the
accelerator opening, the torque of the MT vehicle varies with a
delay in response to a change in the accelerator opening, and the
change speed is slower than the change speed of the torque of the
EV. That is, the torque response of the MT vehicle is lower than
that of the EV. Therefore, even if the EV can be driven like the MT
vehicle by operating a pseudo-device, the same torque response as
that of the EV may give a discomfort to the driver who remembers
the driving feeling of the MT vehicle.
[0009] The present disclosure has been made in view of the above
problems, and an object thereof is to provide an electric vehicle
capable of enjoying both driving like an MT vehicle and driving as
a normal electric vehicle without discomfort.
[0010] The electric vehicle according to the present disclosure is
an electric vehicle using an electric motor as a power device for
traveling, comprising an accelerator pedal, a pseudo-clutch pedal,
a pseudo-gearshift, a mode selector, and a controller. The mode
selector is a device configured to manually or automatically select
a control mode of the electric motor between a first mode and a
second mode. The controller is a device configured to control a
motor torque output by the electric motor in accordance with the
control mode selected by the mode selector.
[0011] The controller comprises a memory and a processor. The
memory stores an MT vehicle model and a motor torque command map.
The MT vehicle model is a model simulating a torque characteristic
of a driving wheel torque in an MT vehicle. The MT vehicle referred
to herein is a vehicle having an internal combustion engine whose
torque is controlled by operation of a gas pedal and a manual
transmission whose gear stage is switched by operation of a clutch
pedal and operation of a gearshift. The MT vehicle model is used in
the first mode. The motor torque command map is a map defining a
relationship of a motor torque with respect to an operation amount
of the accelerator pedal and a rotation speed of the electric
motor. The motor torque command map is used in the second mode.
[0012] When controlling the electric motor in the first mode, the
processor executes the following first to fifth processes. The
first process is a process of receiving an operation amount of the
accelerator pedal as an input of an operation amount of the gas
pedal with respect to the MT vehicle model. The second process is a
process of receiving an operation amount of the pseudo-clutch pedal
as an input of an operation amount of the clutch pedal with respect
to the MT vehicle model. The third process is a process of
receiving a shift position of the pseudo-gearshift as an input of a
shift position of the gearshift with respect to the MT vehicle
model. The fourth process is a process of calculating the driving
wheel torque determined from the operation amount of the gas pedal,
the operation amount of the clutch pedal and the shift position of
the gearshift using the MT vehicle model. Then, the fifth process
is a process of calculating the motor torque for giving the driving
wheel torque to driving wheels of the electric vehicle.
[0013] When controlling the electric motor in the second mode, the
processor executes the following sixth and seventh processing. The
sixth process is a process of disabling the operation of the
pseudo-clutch pedal and the operation of the pseudo-gearshift. The
seventh process is a process of calculating the motor torque using
the motor torque command map based on the operation amount of the
accelerator pedal and the rotation speed of the electric motor.
[0014] Then, the processor controls the electric motor in the first
mode such that responsiveness of the motor torque with respect to a
change in the operation amount of the accelerator pedal is lower
than in the second mode. That is, the processor, in the first mode,
controls the electric motor so as to simulate the response delay of
the torque to the operation of the acceleration pedal occurring in
the MT vehicle with motor torque.
[0015] According to the above configuration, the driver can drive
the electric vehicle like an MT vehicle having an internal
combustion engine and a manual transmission by selecting the first
mode by the mode selector. That is, the driver can enjoy clutch
pedal operation and gearshift operation like an MT vehicle.
Furthermore, in the first mode, torque response delay to the
operation of the accelerator pedal peculiar to the MT vehicle is
also simulated, so that the driver can enjoy driving like the MT
vehicle by the clutch pedal operation and the shift operation
without discomfort.
[0016] As described above, according to the present disclosure, it
is possible to provide an electric vehicle capable of enjoying both
driving like an MT vehicle and driving as a normal electric vehicle
without discomfort.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a diagram schematically illustrating a
configuration of a power system of an electric vehicle according to
an embodiment of the present disclosure.
[0018] FIG. 2 is a block diagram illustrating a configuration of a
control system of the electric vehicle shown in FIG. 1.
[0019] FIG. 3 is a block diagram illustrating functions of the
controller of the electric vehicle shown in FIG. 1.
[0020] FIG. 4 is a diagram illustrating an example of a motor
torque command map provided by the controller shown in FIG. 3.
[0021] FIG. 5 is a block diagram illustrating an example of an MT
vehicle model provided by the controller shown in FIG. 3.
[0022] FIG. 6 is a diagram illustrating an example of an engine
model constituting the MT vehicle model shown in FIG. 5.
[0023] FIG. 7 is a diagram illustrating an example of a clutch
model constituting the MT vehicle model shown in FIG. 5.
[0024] FIG. 8 is a diagram illustrating an example of an MT model
constituting the MT vehicle model shown in FIG. 5.
[0025] FIG. 9 is a diagram illustrating a torque characteristic of
a electrical motor realized in an MT mode in comparison with a
torque characteristic of the electric motor realized in an EV
mode.
[0026] FIG. 10 is a diagram illustrating a response characteristic
of motor torque in the EV mode compared with a response
characteristic of motor torque in the MT mode.
DETAILED DESCRIPTION
[0027] Hereunder, embodiments of the present disclosure will be
described with reference to the drawings. Note that when the
numerals of numbers, quantities, amounts, ranges and the like of
respective elements are mentioned in the embodiments shown as
follows, the present disclosure is not limited to the mentioned
numerals unless specially explicitly described otherwise, or unless
the disclosure is explicitly designated by the numerals
theoretically. Furthermore, structures and steps that are described
in the embodiments shown as follows are not always indispensable to
the disclosure unless specially explicitly shown otherwise, or
unless the disclosure is explicitly designated by the structures or
the steps theoretically.
1. Configuration of Electric Vehicle
[0028] FIG. 1 is a diagram schematically illustrating a
configuration of a power system of an electric vehicle 10 according
to the present embodiment. As shown in FIG. 1, the electric vehicle
10 is provided with an electric motor 2 as a power source. The
electric motor 2 is, for example, a brushless DC motor or a
three-phase AC synchronous motor. The electric motor 2 is provided
with a rotation speed sensor 40 for detecting its rotation speed.
An output shaft 3 of the electric motor 2 is connected to one end
of a propeller shaft 5 via a gear mechanism 4. The other end of the
propeller shaft 5 is connected to a drive shaft 7 at the front of
the vehicle via a differential gear 6.
[0029] The electric vehicle 10 includes driving wheels 8, which are
front wheels, and driven wheels 12, which are rear wheels. The
driving wheels 8 are provided on both ends of the drive shaft 7,
respectively. Each wheel 8 and 12 is provided with a wheel speed
sensor 30. In FIG. 1, only the wheel speed sensor 30 of the
right-hand rear wheel is represented. The wheel speed sensor 30 is
also used as a vehicle speed sensor for detecting the vehicle speed
of the electric vehicle 10. The wheel speed sensor 30 is connected
to a controller 50 to be described later by an in-vehicle network
such as CAN (Controller Area Network).
[0030] The electric vehicle 10 includes a battery 14 and a inverter
16. The battery 14 stores electrical energy that drives the
electric motor 2. The inverter 16 converts DC power input from the
battery 14 to driving power for the electric motor 2. Power
conversion by the inverter 16 is performed by PWM (Pulse Wave
Modulation) control by the controller 50. The inverter 16 is
connected to the controller 50 by the in-vehicle network.
[0031] The electric vehicle 10 includes an accelerator pedal 22 for
inputting an acceleration request and a brake pedal 24 for
inputting a braking request as operation request input devices for
inputting operation requests from the driver to the electric
vehicle 10. The accelerator pedal 22 is provided with an
accelerator position sensor 32 for detecting an accelerator opening
Pap[%] which is an operation amount of the accelerator pedal 22.
The brake pedal 24 is provided with a brake position sensor 34 for
detecting a brake depression amount which is an operation amount of
the brake pedal 24. The accelerator position sensor 32 and the
brake position sensor 34 are connected to the controller 50 by the
in-vehicle network.
[0032] The electric vehicle 10 further includes a pseudo-gearshift
26 and a pseudo-clutch pedal 28 as operation inputting devices. A
gearshift and a clutch pedal are devices that operate a manual
transmission (MT), but of course the electric vehicle 10 is not
equipped with the MT. The pseudo-gearshift 26 and the pseudo-clutch
pedal 28 are dummies that differ from the original gearshift and
clutch pedal.
[0033] The pseudo-gearshift 26 has a structure that simulates a
gearshift installed in an MT vehicle. The arrangement and operating
feeling of the pseudo-gearshift 26 are equivalent to those of the
real MT vehicle. The pseudo-gearshift 26 has positions that
correspond to each gear stage, for example, first-speed stage,
second-speed stage, third-speed stage, fourth-speed stage,
fifth-speed stage, sixth-speed stage, reverse stage, and neutral
stage. The pseudo-gearshift 26 is equipped with a shift position
sensor 36 for detecting gear stage by determining which position
the pseudo-gearshift 26 is in. The shift position sensor 36 is
connected to the controller 50 by the in-vehicle network.
[0034] The pseudo-clutch pedal 28 has a structure that simulates a
clutch pedal installed in the MT vehicle. The arrangement and
operating feeling of the pseudo-clutch pedal 28 are equivalent to
those of the real MT vehicle. When the driver wants to change the
setting of the gear stage by the pseudo-gearshift 26, the driver
depresses the pseudo-clutch pedal 28, and after finishing the
setting change of the gear stage, ceases depressing to release the
pseudo-clutch pedal 28. The pseudo-clutch pedal 28 is equipped with
a clutch position sensor 38 for detecting depression amount Pc[%]
of the pseudo-clutch pedal 28. The clutch position sensor 38 is
connected to the controller 50 by the in-vehicle network.
[0035] The electric vehicle 10 is equipped with a pseudo-engine
speed meter 44. An engine speed meter is a device that displays a
rotation speed of an internal combustion engine to the driver, but
of course, the electric vehicle 10 is not equipped with the
internal combustion engine. The pseudo-engine speed meter 44 is, of
course, a dummy that differs from the original engine speed meter.
The pseudo-engine speed meter 44 has a structure that simulates the
engine speed meter installed in the conventional vehicle. The
pseudo-engine speed meter 44 may be a mechanical type, a liquid
crystal display type, or a projection display type using a head-up
display. In the case of the liquid crystal display type and the
projection display type, a revolution limit may be arbitrarily set
in the pseudo-engine speed meter 44. The pseudo-engine speed meter
44 is connected to the controller 50 by the in-vehicle network.
[0036] The electric vehicle 10 is equipped with a mode selector 42.
The mode selector 42 is a selector for selecting a traveling mode
of the electric vehicle 10. The traveling mode of the electric
vehicle 10 includes an MT mode and an EV mode. The mode selector 42
is configured to be capable of selecting either MT mode or EV mode
arbitrary. Details will be described later, in the MT mode, the
electric motor 2 is controlled in the control mode for driving the
electric vehicle 10 like the MT vehicle (first mode). In the EV
mode, the electric motor 2 is controlled in the normal control mode
for the common electric vehicle (second mode). The mode selector 42
is connected to the controller 50 by the in-vehicle network.
[0037] The controller 50 is typically an ECU (Electronic Control
Unit) mounted on the electric vehicle 10. The controller 50 may be
a combination of a plurality of ECUs. The controller 50 includes an
interface 52, a memory 54, and a processor 56. The in-vehicle
network is connected to the interface 52. The memory 54 includes a
RAM (Random Access Memory) for temporarily recording data and a ROM
(Read Only Memory) for storing a control program executable by the
processor 56 and various data related to the control program. The
processor 56 executes the control program read with the related
data from the memory 54, and generates a control signal based on
the signal obtained from each sensor.
[0038] FIG. 2 is a block diagram illustrating a configuration of a
control system of the electric vehicle 10 according to the present
embodiment. The controller 50 receives signals at least from the
wheel speed sensor 30, the accelerator position sensor 32, the
brake position sensor 34, the shift position sensor 36, the clutch
position sensor 38, the rotation speed sensor 40, and the mode
selector 42. The in-vehicle network is used for communication
between these sensors and the controller 50. Although not shown, in
addition to these sensors, various other sensors are mounted on the
electric vehicle 10, and connected to the controller 50 by the
in-vehicle network.
[0039] Further, from the controller 50, a signal is output to at
least the inverter 16 and the pseudo-engine speed meter 44. The
in-vehicle network is used for communication between these devices
and the controller 50. Although not shown, in addition to these
devices, various other actuators and indicators are mounted on the
electric vehicle 10, and connected to the controller 50 by the
in-vehicle network.
[0040] The controller 50 has a function as a control signal
calculation unit 520. More specifically, the processor 56 functions
at least as the control signal calculation unit 520 when a program
stored in the memory 54 is executed by the processor 56. The
control signal calculation is a function to calculate a control
signal for an actuator or a device. The control signal includes at
least a signal for PWM control of the inverter 16, and a signal for
displaying information on the pseudo-engine speed meter 44. These
functions of the controller 50 will be described below.
2. Functions of Controller
2-1. Motor Torque Calculation Function
[0041] FIG. 3 is a block diagram illustrating functions of the
controller 50 according to the present embodiment, in particular, a
function relating to a calculation of the motor torque command
value for the electric motor 2. The controller 50 calculates the
motor torque command value by the function shown in this block
diagram, and generates the control signal for the PWM control of
the inverter 16 based on the motor torque command value.
[0042] As shown in FIG. 3, the control signal calculation unit 520
comprises an MT vehicle model 530, a required motor torque
calculation unit 540, a motor torque command map 550, and a
changeover switch 560. The control signal calculation unit 520
receives signals from the wheel speed sensor 30, the accelerator
position sensor 32, the shift position sensor 36, the clutch
position sensor 38, the rotation speed sensor 40, and the mode
selector 42. The control signal calculation unit 520 processes the
signals from these sensors and calculates motor torque which the
electric motor 2 is made to output.
[0043] There are two types of calculation of motor torque by the
control signal calculation unit 520: calculation using the MT
vehicle model 530 and the required motor torque calculation unit
540, and calculation using the motor torque command map 550. The
former is used to calculate motor torque when the electric vehicle
10 is to travel in the MT mode. The latter is used to calculate
motor torque when the electric vehicle 10 is to travel in the EV
mode. Which motor torque is used depends on the changeover switch
560. The changeover switch 560 is operated by a signal input from
the mode selector 42.
2-2. Calculation of Motor Torque in MT Mode
[0044] The driving wheel torque of the MT vehicle is determined
from the operation of a gas pedal that controls fuel supply to the
engine, the operation of a gearshift that switches a gear stage of
the MT, and the operation of a clutch pedal that operates a clutch
between the engine and the MT. The MT vehicle model 530 is a model
that calculates the driving wheel torque obtained by operating the
accelerator pedal 22, the pseudo-clutch pedal 28, and the
pseudo-gearshift 26 assuming that the electric vehicle 10 is
equipped with the engine, the clutch, and the MT. Hereinafter, the
engine, the clutch, and the MT, which are imaginarily realized by
the MT vehicle model 530 in the MT mode, will be referred to as an
imaginary engine, an imaginary clutch, and an imaginary MT.
[0045] The MT vehicle model 530 receives a signal of the
accelerator position sensor 32 as an operation amount of the gas
pedal of the imaginary engine. A signal of the shift position
sensor 36 is input to the MT vehicle model 530 as a shift position
of the gearshift of the imaginary MT. Further, a signal of the
clutch position sensor 38 is input to the MT vehicle model 530 as
an operation amount of the clutch pedal of the imaginary clutch.
The MT vehicle model 530 also receives a signal of the wheel speed
sensor 30 as a signal indicating the load condition of the vehicle.
The MT vehicle model 530 is a model simulating the torque
characteristic of the driving wheel torque in the MT vehicle. The
MT vehicle model 530 is configured so that the operation of the
accelerator pedal 22, the pseudo-gearshift 26, and the
pseudo-clutch pedal 28 by the driver is reflected in the value of
the driving wheel torque. The detail of the MT vehicle model 530
will be described later.
[0046] The required motor torque calculation unit 540 converts the
driving wheel torque calculated by the MT vehicle model 530 into a
required motor torque. The required motor torque is the motor
torque required for realizing the driving wheel torque calculated
by the MT vehicle model 530. The reduction ratio from the output
shaft 3 of the electric motor 2 to the driving wheels 8 is used to
convert the driving wheel torque into the required motor torque.
Further, the required motor torque calculation unit 540 receives a
signal from a zero start acceleration request determination unit
500. The content of the determination by the zero start
acceleration request determination unit 500 and the processing by
the required motor torque calculation unit 540 receiving the
determination result from the zero start acceleration request
determination unit 500 will be described later.
2-3. Calculation of Motor Torque in EV Mode
[0047] FIG. 4 is a diagram illustrating an example of the motor
torque command map 550 used for calculating the motor torque in the
EV mode. The motor torque command map 550 is a map to determine the
motor torque using the accelerator opening Pap and the rotation
speed of the electric motor 2 as parameters. A signal of the
accelerator position sensor 32 and a signal of the rotation speed
sensor 40 are input to the respective parameters of the motor
torque command map 550. The motor torque corresponding to these
signals is output from the motor torque command map 550.
2-4. Switching of Motor Torque
[0048] The motor torque calculated using the motor torque command
map 550 is denoted as Tev, and the motor torque calculated using
the MT vehicle model 530 and the required motor torque calculation
unit 540 is denoted as Tmt. The motor torque selected by the
changeover switch 560 among the two motor torques Tev and Tmt is
given as the motor torque command value for the electric motor
2.
[0049] In the EV mode, even if the driver operates the
pseudo-gearshift 26 or the pseudo-clutch pedal 28, the driver's
operation is not reflected in driving of the electric vehicle 10.
In other words, the operation of the pseudo-gearshift 26 and the
operation of the pseudo-clutch pedal 28 are disabled in the EV
mode. However, even while the motor torque Tev is output as the
motor torque command value, the calculation of the motor torque Tmt
using the MT vehicle model 530 is continued. Conversely, the
calculation of the motor torque Tev is continued even while the
motor torque Tmt is output as the motor torque command value. That
is, both the motor torque Tev and the motor torque Tmt are
continuously input to the changeover switch 560.
[0050] By switching the input by the changeover switch 560, the
motor torque command value is switched from the motor torque Tev to
the motor torque Tmt, or from the motor torque Tmt to the motor
torque Tev. At this time, when there is a deviation between the two
motor torques, a torque level difference is generated with
switching. Therefore, for a while after switching, so as not to
cause a sudden change in torque, the gradual change process is
performed on the motor torque command value. For example, in the
switching from the EV mode to the MT mode, the motor torque command
value is not immediately switched from the motor torque Tev to the
motor torque Tmt, it is gradually changed toward the motor torque
Tmt at a predetermined rate of change. The same process is
performed in switching from the MT mode to the EV mode.
[0051] The changeover switch 560 operates in accordance with the
travelling mode selected by the mode selector 42. When the EV mode
is selected by the mode selector 42, the changeover switch 560
connects to the motor torque command map 550 and outputs the motor
torque Tev input from the motor torque command map 550 as the motor
torque command value. When the MT mode is selected by the mode
selector 42, the changeover switch 560 switches a connecting
destination to the required motor torque calculation unit 540.
Then, the changeover switch 560 outputs the motor torque Tmt input
from the required motor torque calculation unit 540 as the motor
torque command value. Such switching of the input is performed in
conjunction with the selection of the traveling mode by the mode
selector 42.
2-5. MT Vehicle Model
2-5-1. Summary
[0052] Next, the MT vehicle model 530 will be described. FIG. 5 is
a block diagram illustrating an example of the MT vehicle model
530. The MT vehicle model 530 comprises an engine model 531, a
clutch model 532, an MT model 533, and an axles and drive wheels
model 534. The engine model 531 is a model of the imaginary engine.
The clutch model 532 is a model of the imaginary clutch. The MT
model 533 is a model of the imaginary MT. The axles and drive
wheels model 534 is a model of the imaginary torque transmission
system from the axles to the driving wheels. Each model may be
represented by a calculation formula or may be represented by a
map.
[0053] Calculation results are input and output between models.
Further, the accelerator opening Pap detected by the accelerator
position sensor 32 is input to the engine model 531. The clutch
pedal depression amount Pc detected by the clutch position sensor
38 is input to the clutch model 532. The shift position Sp detected
by the shift position sensor 36 is input to the MT model 533.
Furthermore, in the MT vehicle model 530, the vehicle speed Vw (or
wheel speed) detected by the wheel speed sensor 30 is used in a
plurality of models. In the MT vehicle model 530, a driving wheel
torque Tw and an imaginary engine speed Ne are calculated based on
these input signals.
2-5-2. Engine Model
[0054] The engine model 531 calculates the imaginary engine speed
Ne and an imaginary engine output torque Teout. The engine model
531 comprises a model to calculate the imaginary engine speed Ne
and a model to calculate the imaginary engine output torque Teout.
For calculating the imaginary engine speed Ne, for example, a model
expressed by the following equation (1) is used. In the following
equation (1), the imaginary engine speed Ne is calculated from a
rotation speed Nw of the wheel 8, a total reduction ratio R, and a
slip ratio Rslip of the imaginary clutch mechanism.
Ne = Nw .times. 1 R .times. Rslip ( 1 ) ##EQU00001##
[0055] In the equation (1), the rotation speed Nw of the wheel 8 is
detected by the wheel speed sensor 30. The total reduction ratio R
is calculated from a gear ratio r calculated by the MT model 533 to
be described later and the reduction ratio specified by the axles
and drive wheels model 534. The slip ratio Rslip is calculated by
the clutch model 532 to be described later. The imaginary engine
speed Ne is displayed on the pseudo-engine speed meter 44 when the
MT mode is selected.
[0056] However, the equation (1) is an equation for calculating the
imaginary engine speed Ne in a condition where the imaginary engine
and the imaginary MT are connected by the imaginary clutch
mechanism. When the imaginary clutch mechanism is disengaged, the
imaginary engine torque Te generated in the imaginary engine can be
regarded as being used to increase the imaginary engine speed Ne.
The imaginary engine torque Te is a torque obtained by adding the
torque due to the moment of inertia to the imaginary engine output
torque Teout. When the imaginary clutch mechanism is disengaged,
the imaginary engine output torque Teout is zero. Therefore, when
the imaginary clutch mechanism is disengaged, the engine model 531
calculates the imaginary engine speed Ne by the following equation
(2) using the imaginary engine torque Te and the moment of inertia
J of the imaginary engine. For the calculation of the imaginary
engine torque Te, a map with the accelerator opening Pap as a
parameter is used.
J .times. 3 .times. 0 .pi. .times. d d .times. t .times. Ne = Te (
2 ) ##EQU00002##
[0057] Incidentally, during idling of the MT vehicle, idle speed
control (ISC control) is executed to maintain the engine speed at a
constant rotation speed. Therefore, the engine model 531 calculates
the imaginary engine speed Ne as a predetermined idling speed (for
example, 1000 rpm), when the imaginary clutch mechanism is
disengaged, the vehicle speed is 0, and the accelerator opening Pap
is 0%. When the driver depresses the accelerator pedal 22 to
perform racing while the vehicle is stopped, the idling speed is
used as the initial value of the imaginary engine speed Ne
calculated by equation (2).
[0058] The engine model 531 calculates the imaginary engine output
torque Teout from the imaginary engine speed Ne and the accelerator
opening Pap. For calculating the imaginary engine output torque
Teout, for example, a two-dimensional map as shown in FIG. 6 is
used. This two-dimensional map is a map defining a relationship
between the accelerator opening Pap in steady-state, the imaginary
engine speed Ne, and the imaginary engine output torque Teout. In
this map, imaginary engine outputting torque Teout for imaginary
engine speed Ne is given for each accelerator opening Pap. The
torque characteristic shown in FIG. 7 can be set to the
characteristic assumed for a gasoline engine or can be set to that
assumed for a diesel engine. In addition, the torque characteristic
can be set to that assumed for a natural intake engine or can be
set to that assumed for a turbocharged engine. For example, an HMI
(Human Machine Interface) unit may be installed near an instrument
panel so that the driver can chose a preferred setting of the
imaginary engine of the MT mode by operating the HMI unit. The
imaginary engine output torque Teout calculated by the engine model
531 is output to the clutch model 532.
[0059] Incidentally, in general, the torque output by the engine
has a response delay with respect to a change in the accelerator
opening. The response delay of the torque in the engine is
remarkably large even in comparison with the response delay of the
torque in the electric motor. Therefore, in the engine model 531,
the response delay of the torque originally possessed by the engine
is also simulated. That is, the engine model 531 is configured so
that the imaginary engine output torque Teout output from the
engine model 531 varies with a delay in response to a change in the
accelerator opening Pap input to the engine model 531. The response
characteristic of the imaginary engine output torque Teout to the
accelerator opening Pap in the engine model 531 can be approximated
simply by a transfer function having a dead time element and a
first order lag element.
[0060] Furthermore, the response characteristic of the torque to
the accelerator opening also differs depending on the type of the
engine. For example, the response characteristic of the torque to
the accelerator opening are different between a gasoline engine and
a diesel engine. Even in the same gasoline engine, the response
characteristic of the torque to the accelerator opening is
different between a natural aspiration engine and a supercharged
engine. In addition, the response characteristic of the torque to
the accelerator opening is different between a racing engine and an
engine of a general passenger vehicle. It is believed that if the
driver can arbitrarily change the type of the engine that the
engine model 531 simulates, the driver will be able to enjoy
driving in the MT mode more. The type of the engine may be
selected, for example, with the HMI unit described above. Then,
depending on the type of the engine selected, for example, each of
the dead time element and the first order lag element in the
transfer function may be changed.
2-5-3. Clutch Model
[0061] The clutch model 532 calculates a torque transmission gain
k. The torque transmission gain k is a gain for calculating the
torque transmission degree of the imaginary clutch corresponding to
the depression amount of the pseudo-clutch pedal 28. The clutch
model 532 has, for example, a map as shown in FIG. 7. In this map,
the torque transmission gain k is given for the clutch pedal
depression amount Pc. In FIG. 7, the torque transmission gain k is
1 when the clutch pedal depression amount Pc is in the range from
Pc0 to Pc1, the torque transmission gain k monotonically decreases
at a constant slope when the clutch pedal depression amount Pc is
in the range from Pc1 to Pc2, and the torque transmission gain k is
0 when the clutch pedal depression amount Pc is in the range from
Pc2 to Pc3. Here, Pc0 corresponds to the position where the clutch
pedal depression amount Pc is 0%, Pc1 corresponds to the position
of the play limit when the clutch pedal is depressed, Pc3
corresponds to the position where the clutch pedal depression
amount Pc is 100%, and Pc2 corresponds to the play limit when the
clutch pedal is returned from Pc3.
[0062] The map shown in FIG. 7 is an example. The change in the
torque transmission gain k with respect to an increase in the
clutch pedal depression amount Pc is not limited to the change
curve shown in FIG. 8 as long as it is a broad monotonic decrease
toward 0. For example, the change in the torque transmission gain k
in the range from Pc1 to Pc2 may be a monotonically decreasing
curve that is convex upward or a monotonically decreasing curve
that is convex downward.
[0063] The clutch model 532 calculates a clutch output torque Tcout
using the torque transmission gain k. The clutch output torque
Tcout is the torque output from the imaginary clutch. The clutch
model 532 calculates the clutch output torque Tcout from the
imaginary engine output torque Teout and the torque transmission
gain k by, for example, the following equation (3). The clutch
output torque Tcout calculated by the clutch model 532 is output to
the MT model 533.
Tcout=Teout.times.k (3)
[0064] Further, the clutch model 532 calculates the slip ratio
Rslip. The slip ratio Rslip is used to calculate the imaginary
engine speed Ne in the engine model 531. The slip ratio Rslip can
be calculated by using a map in which the slip ratio Rslip is given
to the clutch pedal depression amount Pc, in the same manner as the
torque transmission gain k. Instead of such a map, the slip ratio
Rslip may be calculated from the torque transmission gain k by the
following equation (4) representing a relation between the slip
ratio Rslip and the torque transmission gain k.
Rslip=1-k (4)
2-5-4. MT Model
[0065] The MT model 533 calculates the gear ratio r. The gear ratio
r is the gear ratio determined from the shift position Sp of the
pseudo-gearshift 26 in the imaginary MT. The shift position Sp of
the pseudo-gearshift 26 and the gear stage of the imaginary MT are
in a one-to-one relation. The MT model 533 has, for example, a map
as shown in FIG. 8. In this map, the gear ratio r is given for the
gear stage. As shown in FIG. 8, the larger gear stage, the smaller
the gear ratio r.
[0066] The MT model 533 calculates a transmission output torque
Tgout using the gear ratio r. The transmission output torque Tgout
is the torque output from the imaginary transmission. The MT model
533 calculates the transmission output torque Tgout from the clutch
output torque Tcout and the gear ratio r by, for example, the
following equation (5). The transmission output torque Tgout
calculated by the MT model 533 is output to the axles and drive
wheels model 534.
Tgout=Tcout.times.r (5)
2-5-5. Axles and Drive Wheels Model
[0067] The axles and drive wheels model 534 calculates the driving
wheel torque Tw using a predetermined reduction ratio rr. The
reduction ratio rr is a fixed value determined by the mechanical
structure from the imaginary MT to the driving wheels 8. The value
obtained by multiplying the reduction ratio rr by the gear ratio r
is the total reduction ratio R described above. The axles and drive
wheels model 534 calculates the driving wheel torque Tw from the
transmission output torque Tgout and the reduction ratio rr by, for
example, the following equation (6). The driving wheel torque Tw
calculated by the axles and drive wheels model 534 is output to the
required motor torque calculation unit 540.
Tw=Tgout.times.rr (6)
2-6. Torque Characteristic of Electric Motor Realized in MT
Mode
[0068] The required motor torque calculation unit 540 converts the
driving wheel torque Tw calculated by the MT vehicle model 530 into
motor torque. FIG. 9 is a diagram illustrating the torque
characteristic of the electric motor 2 realized in the MT mode, and
in particular, the characteristic of the motor torque with respect
to the motor speed, as compared with the torque characteristic of
the electric motor 2 realized in the EV mode. In the MT mode, as
shown in FIG. 9, it is possible to realize a torque characteristic
(solid line in the drawing) such as to simulate the torque
characteristic of the MT vehicle according to the gear stage set by
the pseudo-gearshift 26.
2-7. Comparative of Motor Torque Response Characteristics
[0069] FIG. 10 is a diagram illustrating a response characteristic
of the motor torque in the EV mode compared with a response
characteristic of the motor torque in the MT mode. As shown by the
broken line in the lower graph, the motor torque output by the
electric motor 2 in the EV mode responds substantially linearly to
the accelerator opening. This is the response characteristic of the
motor torque which the electric motor 2 originally has. Therefore,
in the EV mode, the driver can enjoy the driving feeling unique to
the EV, which is realized by the linear response characteristic of
the motor torque.
[0070] On the other hand, the motor torque in the MT mode changes
as shown by a solid line in the lower graph, with respect to a
change in the accelerator opening shown in the upper graph. As
explained in "2-5-2. Engine model", the engine model 531 is
configured to simulate the response delay of the torque that the
real engine has. Therefore, the motor torque output by the electric
motor 2 in the MT mode begins to change delayed from the change in
the accelerator opening, and the rate of change is also suppressed
as compared with the motor torque in the EV mode. In this way, the
motor torque in the MT mode changes with responsiveness similar to
the torque output by the engine.
[0071] As described above, the responsiveness of the motor torque
to the accelerator opening in the MT mode is lower than that of the
motor torque to the accelerator opening in the EV mode. By
realizing such a response characteristic of the motor torque in the
MT mode, the driver can enjoy both driving like the MT vehicle and
driving as the normal EV without discomfort in the electric vehicle
10.
3. Other
[0072] The electric vehicle 10 according to the above embodiment is
an FF vehicle that drives the front wheels in one electric motor 2.
However, the present disclosure is also applicable to an electric
vehicle in which two electric motor are arranged in front and rear
to drive each of the front and rear wheels. The present disclosure
is also applicable to an electric vehicle comprising an in-wheel
motor on each wheel. The MT vehicle model of these cases may be a
model in which an all-wheel-drive vehicle with MT is modeled.
[0073] The electric vehicle 10 according to the above embodiment is
not provided with a transmission. However, the present disclosure
is also applicable to an electric vehicle having a stepped or
continuously variable automatic transmission. In this case, the
power train consisting of the electric motor and the automatic
transmission may be controlled so as to output the motor torque
calculated by MT vehicle model.
[0074] In the above embodiment, the switching of the selection of
the MT mode and EV mode is performed by the mode selector 42. The
mode selector 42 is a device for manually selecting the traveling
mode. However, a mode selector selecting the traveling mode
automatically may be provided. For example, the traveling mode may
be selected automatically based on peripheral information of the
self vehicle acquired by the external sensors such as the camera or
the LIDAR or location information on a map that can be acquired by
a navigation device.
[0075] Incidentally, in the MT vehicle, a shock occurs when the
clutch mechanism is suddenly engaged. In order to simulate this
shock in the electric vehicle 10, the response rate of the torque
of the electric motor 2 may be equal to or faster than that of the
EV mode when the driver suddenly returns the depression of the
pseudo-clutch pedal 23 in the MT mode.
* * * * *